ABSTRACT Sepsis is a leading cause of morbidity and mortality in the United States, affecting over 750,000 Americans each year at an annual cost of over $20 billion. Several medical treatments are of proven effectiveness in this population, including timely administration of antibiotics and early resuscitation with intravenous fluids. However these treatments are inconsistently applied, creating an important quality gap. Protocols for early recognition and treatment can help close this gap and save lives in patients with sepsis, and in turn policy makers are increasingly using legal mechanisms to incentivize the use of sepsis protocols. One such initiative is an unprecedented set of New York State regulations implemented in June of 2013 and collectively known as ?Rory's Regulations?. Named after Rory Staunton, a 12-year-old boy who died of sepsis at a New York hospital, Rory's Regulations mandate that all hospitals in the state implement evidence-based protocols for sepsis management and report data on sepsis protocol adherence and outcomes to the state government. Rory's Regulations are an innovative strategy for policy-based quality improvement in that they link traditional quality reporting with specific mandates for evidence-based practice. They are also a leading-edge forerunner to sepsis regulations in development in other states and at the national level, making it imperative that we understand their clinical and financial impact. The overall goal of this proposal is to systematically evaluate the impact of the New York state sepsis regulations. We plan a novel mixed methods approach designed to yield information that policy makers can use not only to refine the existing policy but also to design and implement future polices. First, we will use hospital emergency department and inpatient data from New York and eight control states to assess the effects of the 2013 regulations on mortality, complications of care, health care utilization and costs, controlling for case-mix and temporal trends. Second, we will complement our quantitative analyses with a theory-driven qualitative analysis in which we will perform and analyze semi-structured interviews with key stakeholders in New York State, including clinicians, policy-makers, and patient advocates. This qualitative analysis will serve to help interpret the overall policy effects and provide actionable guidance to policy makers seeking to develop similar sepsis-related regulations. Together, these aims will comprise the first rigorous evaluation of a landmark set of state-wide sepsis regulations. More broadly, they will be the first evaluation of a novel strategy for state-wide quality improvement through policy mandates for specific evidence-based practices, directly informing future efforts to improve the quality of care not only in sepsis but also in other aspects of hospital medicine.